/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.phoenix.expression;

import java.util.List;

import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.query.QueryConstants;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.schema.types.PDate;
import org.apache.phoenix.schema.types.PLong;



/**
 * 
 * Subtract expression implementation
 *
 * 
 * @since 0.1
 */
public class LongSubtractExpression extends SubtractExpression {
    public LongSubtractExpression() {
    }

    public LongSubtractExpression(List<Expression> children) {
        super(children);
    }

    @Override
	public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
		long finalResult=0;
		
		for(int i=0;i<children.size();i++) {
		    Expression child = children.get(i);
            if (!child.evaluate(tuple, ptr) || ptr.getLength() == 0) {
                return false;
            }
            PDataType childType = child.getDataType();
            boolean isDate = childType.isCoercibleTo(PDate.INSTANCE);
            long childvalue = childType.getCodec().decodeLong(ptr, child.getSortOrder());
            if (i == 0) {
                finalResult = childvalue;
            } else {
                finalResult -= childvalue;
                /*
                 * Special case for date subtraction - note that only first two expression may be dates.
                 * We need to convert the date to a unit of "days" because that's what sql expects.
                 */
                if (isDate) {
                    finalResult /= QueryConstants.MILLIS_IN_DAY;
                }
            }
		}
		byte[] resultPtr=new byte[getDataType().getByteSize()];
		getDataType().getCodec().encodeLong(finalResult, resultPtr, 0);
		ptr.set(resultPtr);
		return true;
	}

	@Override
	public final PDataType getDataType() {
		return PLong.INSTANCE;
	}

    @Override
    public ArithmeticExpression clone(List<Expression> children) {
        return new LongSubtractExpression(children);
    }
	
}
